C#: Tracer support for invoking csc directly.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Extractor/CompilerVersion.cs

@@ -74,7 +74,9 @@ public CompilerVersion(Options options)
                     specifiedFramework = compilerDir;
                 }
 
-                var versionInfo = FileVersionInfo.GetVersionInfo(SpecifiedCompiler);
+                // If csc is specified as compiler name, then attempt to read the version information from csc.dll
+                var compilerBinaryName = SpecifiedCompiler.EndsWith("csc") ? $"{SpecifiedCompiler}.dll" : SpecifiedCompiler;
+                var versionInfo = FileVersionInfo.GetVersionInfo(compilerBinaryName);
                 if (!knownCompilerNames.TryGetValue(versionInfo.OriginalFilename ?? string.Empty, out var vendor))
                 {
                     SkipExtractionBecause("the compiler name is not recognised");

csharp/tools/tracing-config.lua

@@ -226,6 +226,11 @@ function RegisterExtractorPack(id)
             prepend = { '--compiler', '"${compiler}"' },
             order = ORDER_BEFORE
         }),
+        CreatePatternMatcher({ '^csc$' }, MatchCompilerName,
+            extractor, {
+            prepend = { '--compiler', '${compiler}' },
+            order = ORDER_BEFORE
+        }),
         MsBuildMatcher,
         function(compilerName, compilerPath, compilerArguments, _languageId)
             -- handle cases like `dotnet exec csc.dll <args>` and `mono(-sgen64) csc.exe <args>`